Once a year, as another December gives way to a chill January, Chief Justice John Roberts rereads a poem published in 1749 by the great writer, moralist and late-night conversationalist Samuel Johnson. Roberts began the ritual in the 1970s as an undergraduate at Harvard, where he was one of many students taught to revere Johnson by the master biographer Walter Jackson Bate.

It is an odd pairing, not least because Roberts comes off as upbeat as a roomful of Rotarians, while Johnson, despite his vast accomplishments--including singlehandedly compiling the first comprehensive dictionary of the English language--was haunted by the inevitability of...